The invention concerns a device for dosed dispensing of flowable material components, with supply containers receiving the material components, and having an outlet and with at least one removal means with an inlet, wherein the material components can be removed in batches from the supply container by means of a screw and a controllable drive, and the removal means and the supply container can be moved relative to each other, wherein the inlet of the removal means can be docked to the outlet of the supply container.
Flowable material components, such as powder or granulated bulk material, which are provided in supply containers, require dosed dispensing of the components for their intended use, in particular, when the dosed material components are to be dispensed, in correspondence with a predetermined recipe, to a mixer, a processing machine e.g. an extruder, an injection molding machine, a tablet-compressing machine, a packing machine, a conveyor or the like.
To detect the mass throughput of the discharged material components, the prior art supply containers have a feed screw on their outlet side (EP 0 344 521). The feed screw is driven by a motor and disposed downstream of the outlet of the supply container which is formed e.g. as a silo, such that a desired quantity of the material component can be removed from the supply container. Dosing is effected volumetrically through the number of revolutions of the feed screw or gravimetrically, wherein the material component is transferred to a weighing container and the feed screw is stopped as soon as the weighing container contains the desired amount of material. These systems are demanding and expensive since each supply container has its own screw drive, and inefficient, in particular for containers having a relatively small volume, e.g. for the allocation of chemicals, colorants, pharmaceutical substances etc.
Moreover, conventional removal means comprising feed screws with controllable drive (DE 199 41 920) receive the material components to be dosed e.g. via a charging funnel. Dosing is also effected volumetrically through the number of revolutions of the screw or gravimetrically by transferring the material component into a weighing container via the screw. Disadvantageously, the material remaining in the feed screw after dosing of a material component must be disposed of and the use of such a removal means for dosed allocation of different material components produces undesired cross-contamination in the feed screw.
These disadvantages are eliminated in accordance with a prior suggestion of the Assignee which was not previously published (DE 102 20 792, EP 03006459) in that the feed screw is disposed in the region of the outlet and within the supply container without drive but rotatable and has a coupling means on the outlet side, wherein the inlet region of the removal means has a controllable drive whose drive shaft has a terminal coupling means which can be connected to the coupling means of the screw for secure mutual rotation therewith, and the screw coupling means also has a closing piece sealing the outlet of the supply container.
This design permits exact dosing of the material component to be removed from the respective supply container by docking the inlet of the removal means to the outlet of the supply container and connecting the coupling means of the removal means drive shaft to the coupling means of the otherwise undriven screw, in the region of the outlet of the supply container. The screw is then set into rotation via the drive shaft by the controlled drive of the removal means thereby transferring the material component from the supply container outlet via the inlet into the removal means. As soon as the desired amount of the material component has been removed from the supply container, the drive shaft is stopped, decoupled from the screw and the removal means is moved away from the outlet of the supply container. The dosed allocation can be conventionally provided volumetrically through control of the number of rotations of the drive shaft connected to the screw or gravimetrically by a weighing container connected downstream of the removal means. Since the screw remains in the outlet of the supply container, the entire removed material can be supplied for its intended use, thereby avoiding cross-contamination. The drive-less arrangement of the screw in the region of the outlet of each supply container permits extremely inexpensive production thereof compared to supply containers having their own downstream motor driven screw such that the supply container can e.g. be constructed as a portable, one-way container. The supply container may of course also be a stationary or displaceable container or a silo with an outlet disposed on the lower side of the container, wherein, in particular, several supply containers are provided and the removal means may be displaceable between the outlets of the supply containers to remove the desired amounts of the various material components provided in these containers. The above-described device is suitable, in particular, for batch-like sequential supply of different material components provided in several supply containers, e.g. plastic granulated matter of different types or colors, additives, colorants, pharmaceutical agents etc. which are to be fed to a mixer or a processing machine according to a predetermined recipe.
In view of this previously unpublished suggestion of the Assignee, it is the underlying purpose of the present invention to guarantee safe transfer of the material components.